Delivering TV Over DSL

BY DANNA BETHLEHEM

According to a recent study by the DSL Forum, at the end of the first quarter 2003 there were 41.3 million DSL lines deployed worldwide. The biggest growth spurt occurred in Asia. In the U.S., the latest round of data released by the FCC on broadband infiltration shows a 55 percent increase in the number of high-speed lines installed in 2002, with DSL and cable growing at a similar rate. This move toward broadband is having an impact on the way TV is being delivered.

The rollout of digital networking infrastructure coupled with deregulation, is opening the door for telcos and operators to offer converged "Triple Play" services comprising broadband telephony, Internet access and TV (or video). TV over IP, as opposed to traditional cable or broadcast and satellite TV, utilizes digital broadband networks such as ADSL, VDSL, fiber, LMDS and wireless LANs to transmit programming to consumers' homes. Telcos are delivering TV over their IP networks for regular TV services, time-shifted TV or personal video recorder (PVR) services, Interactive TV and TV to the desktop. This last application is one of the hallmarks of TV over IP versatility. Viewers can watch TV on their PCs or on their TVs.

Telcos and operators have had no choice but to tread the IP road. Deregulation has increased competition in their traditional telephony markets. The threat is not only coming from the cable companies, but also from mobile services, which have reduced the number of land-based phone lines that many households need. Likewise, the growing prevalence of broadband Internet access is making a second dial-up line unnecessary in many homes. Telcos are adopting TV over IP strategies as a pro-active stance, before cable companies start infringing on their traditional revenue channels, and also as a way of justifying DSL offerings. Based on this approach, for some telcos it is not financially viable to offer plain broadband intended for Internet use, without the additional TV over IP service. By streaming TV over their native infrastructures, telcos have a chance to recoup or gain market share and increase revenues by offering a wider range of services.

With TV over IP, operators can offer a greater level of service to their customers. The fact that customers receive converged services on a single pipe and interface with a single provider for all communication needs results in easier technical maintenance, streamlined billing and improved customer service. In this regard, many telcos are in a good position to capitalize on the high level of existing service that they offer their customers. What's more, by utilizing digital networks, telcos and operators can offer far more sophisticated programming packages. It is possible to target specific channels at small groups of viewers, based on pre-defined viewing profiles.

GETTING TV OVER PHONE LINES: DSL APPLICATION ARCHITECTURE
Streaming TV over DSL lines is possible by using high quality MPEG video. The various MPEG standards allow application developers to create customized trade-offs between playback rate, quality, bandwidth and cost.

MPEG-1, MPEG-2 and MPEG-4 offer different compression rates and schemes, allowing service providers to offer various video streaming services:

• MPEG-1 provides very good quality at playback rates of up to three Mbps;
• MPEG-2 provides a compression solution for applications that are not limited by bandwidths (three to 15 Mbps). Such a broad compression range means that it is not necessary to sacrifice quality to compression rate limitations; and
• MPEG-4 is a set of compression/decompression formats and streaming technologies that address the need for distributing rich interactive media over narrow and broadband networks. Although MPEG-4 covers more or less the same encoding range as MPEG-1 and MPEG-2, its target applications are different. MPEG-4 defines interactivity, scalability and streaming of rich media. Content compressed according to the MPEG-4 standard can be streamed over the broad or narrowband Internet, used in Interactive TV applications or streamed to wireless appliances such as cellular phones and PDAs (Personal Digital Assistants).

DSL is well suited for TV over IP. It provides sufficient bandwidth and bi-directional communication for management applications, such as billing and interactivity. DSL incorporates forward error correction that dramatically reduces errors caused by impulse noise. Most important: Since DSL modems are installed on existing copper lines, there is no need for massive re-wiring. Thus, the cost of initial deployment is financially feasible.

ADSL
ADSL can support last-mile bandwidths between 512 Kbps and 8 Mbps. The actual bandwidth available depends on the distance between the end point and the ADSL DSLAM. Depending on the last mile bandwidth available, users can receive two channels of video. In this case, two IP STBs (Set-Top-Boxes) will reside at the end point (one STB for each channel).

An important part of the central office configuration is making sure that the ADSL DSLAM supports multicast. If it doesn't, then the level III device has to replicate all streams for each channel requested. This is liable to cause congestion at the DSLAM. For example, if the DSLAM at the central office services 20 end points and all end points request channel three, then the level III device has to feed channel three into the DSLAM 20 times. If on the other hand the DSLAM supports multicast, it would receive one stream of channel three and replicate it for each end point.

VDSL
VDSL is an optimal network infrastructure for TV over IP services. VDSL configuration rests on fiber connectivity over the backbone at bit rates of 155 Mbps and up. Transmission from the last mile network node to the end point is at bit rates of between 10 and 40 Mbps. The high bandwidths supported by VDSL enable consumers to receive multiple channels for playback on multiple TV sets. With VDSL, the backbone infrastructure is based on fiber to the curb/basement while the last mile solution uses VDSL over the copper telephone line.

FIBER TO THE HOME (FTTH)
Another very suitable infrastructure is Fiber to the Home (FTTH). FTTH configuration rests on fiber connectivity from the video IP head-end to the end point. In this configuration, video is transmitted over a fiber backbone at more than 155 Mbps. Last mile configuration consists of a 100Base-T network. Such wide bandwidths allow users to receive multiple channels, which are played back by IP set-top boxes.

Nuts and Bolts
When implemented by a telco or operator, a TV over IP solution would typically stream between 50 and 150 TV channels over an IP network. Content is streamed from the operator's IP head-end over the backbone to a central/regional office. At the central office, the video is distributed over the "last mile" to the consumer's home. Complimentary streaming equipment at the central office allows operators to insert additional channels of local content, which can be targeted at specific areas or groups of users. At the consumer's home, an IP set-top box displays the video stream on a TV set.

Transparent Delivery
At the end of the day, people in their living rooms don't really care what type of network delivers their favorite show. What they do care about is quality and added value services. This is where TV over IP can influence consumers' levels of expectations. Telcos or operators that offer "triple play" services comprising of telephony, high-speed Internet, and advanced digital TV services can provide real added value to their customers.

Danna Bethlehem is publications and online marketing manager for Optibase, Ltd. Optibase is a pioneer and market leader in broadband media gateways and MPEG-1 and MPEG-2 encoding and streaming platforms. Propelled by sophisticated technology and market expertise, Optibase's products are at the core of professional digital video solutions worldwide. Optibase's products enable applications such as TV entertainment over IP networks, digital video archiving, distance learning and business television. They also serve the professional video market for high-end content creation applications. Optibase products are marketed in over 40 countries through a combination of direct sales, independent distributors, system integrators and OEM partners. For more information, please visit www.optibase.com.